The present invention relates to a safety belt arrangement with a controllable blocking apparatus that is controlled sensitive to the vehicle and/or to the safety belt, and with a safety belt buckle and with a tensioning apparatus inserted in the safety belt arrangement, which tensioning apparatus when triggered eliminates the slack in the belt, and with a continuously working device for limiting the force exerted on the safety belt by the forward displacement of the belted occupant.
Prior art includes a retractor described in DE-OS 19 13 448 as a blocking apparatus with a tensioning apparatus associated with the retractor; in the known device, during normal driving the belt shaft is associated with a lockable tensioning spring as tensioning apparatus that is triggered when a predetermined dangerous vehicle deceleration occurs, whereby the end of the tensioning spring associated with the belt shaft engages the belt shaft by means of a tension coupling that is triggerable during dangerous situations so that the tensioning spring causes the slack in the safety belt to be taken up on the belt shaft in the tensioning direction.
Once the tensioning procedure has concluded, there is a blocking condition in which substantial forces can disadvantageously occur when the body of the occupant belted in can xe2x80x9cfall into the beltxe2x80x9d due to the acceleration or deceleration forces exerted on him so that retention by means of the safety belt entails a risk of injury. For avoiding this, the safety belt retractor known from DE-OS 19 13 448 is provided a continuously functioning force limiting device that, during the load on the safety belt that occurs subsequent to the tensioning motion, permits a limited belt release by rotating the belt shaft in the unwinding direction of the safety belt.
The known embodiment of the safety belt arrangement is associated with the disadvantage that when the tensioning process and the force limiting process overlap, as can occur during a serious accident when the safety belt is somewhat slack, the force limiting device can be triggered during the tensioning process and thus the established preliminary displacement path of the force limiting device can be used up and thus the winding path of the tensioning apparatus can be made to compensate. That is, if there is already a high load on the safety belt in the unwinding direction by a premature displacement of the belted occupant during the tensioning process effective in the winding direction of the safety belt, such a high load can build up in the safety belt that the force limiting device becomes operative and a corresponding belt release is permitted at the same time as the belt retraction initiated by the tensioning apparatus.
The object of the present invention is therefore to avoid an overlap in the tensioning process and the force limiting process in a safety belt arrangement of the type cited in the foregoing.
This object is achieved, including advantageous embodiments and further developments of the present invention, from the contents of the patent claims that follow this specification.
The main idea behind the invention is to provide a time-controlled device for actively turning off the drive of the tensioning apparatus after a predetermined time period has elapsed.
Known from DE 43 31 027 A1 is a safety belt arrangement with a retractor, a tensioning apparatus coupled thereto, and a force limiting device, in which safety belt arrangement suitable means ensure that the force limiting device does not function until the tensioning motion has concluded, whereby the force limiting device is turned off during normal blocking of the self-blocking retractor and does not become ready to function until there is a tensioning motion. This ensures that during an accident that does not trigger activation of the tensioning apparatus, the force limiting device is not switched on and therefore is not functional, because in such cases even limited preliminary displacement of the occupant is not permitted. Such preliminary displacement is only permissible when the belt lies taut against the body, which means that the force limiting device does not switch on until after the tensioning motion has concluded. Although overlap of the tensioning process and force limiting process is prevented in such a safety belt arrangement, this requires that a coupling between the retractor and the force limiting device be turned on, and not only is this complex in terms of manufacture and assembly, it also entails the disadvantage of a malfunction in such a provided coupling.
Thus the present invention advantageously focuses on preventing the tensioning process and the force limiting process from overlapping in a continuously functioning force limiting device. In addition, the present invention is not limited to the cooperation of a tensioning apparatus with a retractor, but rather can be employed with any type of tensioning apparatus, for instance even with a lock tensioner, and with any type of force limiting device, that is, for instance, with a force limiting device that can be inserted in the safety belt itself if the drive of the tensioning apparatus is rendered non-functional after a predetermined period of time. Thus the drive of the tensioning apparatus is turned off early enough that the force critical for triggering the force limiting device cannot build up in the safety belt arrangement even if there is a possible early preliminary displacement of the belted occupant during the tensioning process.
In accordance with one exemplary embodiment of the present invention, it is provided that the time measurement for the predetermined period of time is activated by a central sensor, known per se, for controlling the components in the safety belt arrangement, as such a central sensor is used for triggering the airbag arranged in a vehicle or for triggering tensioning apparatus; thus the drive of the tensioning apparatus is deactivated independent of all of the parameters for tensioning the belt, such as ignition time for the drive, tensioning path, belt slack, tensioning force, after a predetermined time period of about 6 to 12 milliseconds, so that during the period of the accident event subsequent thereto the force limiting device can begin to function with no interference. This means that the focus is on the beginning of the accident event determined by the central sensor of the vehicle, and this is particularly advantageous when the force level of the force limiting device is set low.
In accordance with one exemplary embodiment of the present invention, it can be provided that the time measurement for the predetermined time period is activated by triggering the tensioning apparatusxe2x80x94for instance by the gas pressure that occurs or by the movement of corresponding drive means.
In one embodiment, the invention provides that the predetermined time period for turning off the drive in the tensioning apparatus is variably adjustable. Thus, in accordance with one exemplary embodiment of the invention, the setting of the predetermined time period depending on the deformation characteristics of the type of vehicle during an accident can be one influencing variable for the setting of the predetermined time period. It is also possible to modify or adapt the setting of the predetermined time period during the accident event depending on the detected accident conditions such as, for instance, the severity of the accident or the seated distance from the steering wheel or dashboard as other parameters.
Once the predetermined time period for deactivation has elapsed, in accordance with one exemplary embodiment of the present invention, the drive for the tensioning apparatus can be turned off via a sudden release of the drive. To this end it can be provided that the pipe that conducts the propellant gases generated by the drive for the tensioning apparatus has a relief aperture that is closed off via a valve that can be opened after the predetermined time period has elapsed. In accordance with exemplary embodiments of the present invention, the valve can comprise a stopper comprising pyrotechnic material, which stopper has a burn-out duration that equals the predetermined time period for turning off the drive for the tensioning apparatus, or it can be provided that the valve comprises a valve cover that closes off the relief aperture in the pipe, whereby the valve cover can be removed from the relief aperture by an external force.
In one alternative embodiment of the present invention, it can be provided that a sudden interruption in the flux of force between the drive for the tensioning apparatus to the part in the safety belt arrangement that tautens the belt turns off the drive for the tensioning apparatus.
When, in accordance with one exemplary embodiment of the present invention, the tensioning apparatus can be coupled to the belt shaft of the blocking apparatus by means of a pawl coupling, as described in DE 43 31 027 A1, it can be provided that the coupling provided between the shaft and the tensioning apparatus can be made to engage the associated counterpart by means of an actuator and can be returned to an unengaged position once the predetermined time period has elapsed.
In one embodiment of a safety belt arrangement in which the tensioning apparatus acts by means of mass bodies accelerated by the drive of the tensioning apparatus on a pinion arranged on the belt shaft of the blocking apparatus, as disclosed in WO 95/27638 for instance, it can be provided that the belt shaft and pinion are mutually engaged by at least one catch, and that after the predetermined time period has elapsed the catch can be disengaged from the pinion via an associated actuator.
When, in accordance with exemplary embodiments of the present invention, it is provided that the valve cover moves or that there is an interruption in the flux of force from the drive for the tensioning apparatus to the part that performs the belt tensioning, in accordance with alternative exemplary embodiments of the invention, the external force to be additionally applied can be applied mechanically, electrically, or pyrotechnically using suitable drive elements, whereby these drive elements can be rendered functional by a time control.